Being a total electronic toy geek, I naturally have a few laser pointers laying around. One of them disassembles nicely into a compact piece about an inch and a quarter long, with easy leads for the power supply and a nice push-button switch all wrapped up in the bundle. I took this bit and soldered it to a battery holder from a toy FM radio, yielding this beauty:
The battery pack is hidden away inside one of the side compartments. This allows the laser to be powered independently of the rest of the droid, which decreases the chances that I'll screw something up in the inner circuitry. It also makes changing the laser batteries nice and convenient, while still outwardly invisible.
Surgery was the next point on the agenda. Specifically, I needed to actually find a place to put the laser eye, so I drilled out one of the decorative, non-functional bits on the head dome. Well, "drilled" is a dishonest term - a more accurate description would be "hacked away with a pocket knife".
This yields a nice little cubbyhole for the laser to stick out of:
There's still some superglue work to be done (i.e. making the battery pack actually stay inside the compartment), and the laser needs an external switch. My plan at the moment is to put a push-toggle switch on the top of the dome; one of the blue panels is removable so you can put R2's little spy antenna up there. I'm thinking of hiding the switch under that panel.
Once that's done, it's just a bit of reassembly work, and I have my customized Terminator-D2 ready for action.